"I have to make sure people are managing the way I want them to manage, and consistently across the company. I worked on [course planning] for five or six months and eventually built it into this three-segment course that I teach over two days. Those are great teaching moments when the CEO is standing in front of you and saying, 'here's a great example of someplace I screwed this up.'"

Costolo has some very particular views about management, and there's no more powerful way of driving them home than personally delivering them. And clearly, he makes it a priority to explain failures instead of just successes, which can be a much more powerful tool.

People who are hired for new management positions likely have a fair amount of experience outside of Twitter. Rather than expecting them to adapt on their own, he makes it a priority to personally connect and explain what he expects, which leads to a more consistent management style and culture.

New hires perform poorly when they're uncertain. This is a way for Costolo to ensure that new managers not only know the values and practices he advocates, but really listen to them.